The present invention relates to a filter assembly for filtering of electrical signals, and to a filtered electrical connector including such a filter assembly. In particular, the present invention relates to a filtered electrical connector with adjustable performance using combined multi-aperture ferrite cores.
Filtered electrical connectors are known. Conventional filtered electrical connectors use a ferrite bead or a coil, or both, for attenuating and filtering electrical signals directed through the electrical connector. Coils provide filtering functions which show very distinct peaks of attenuation at certain (resonance) frequencies while the filtering performance between the peaks is poor. Ferrite beads provide a more uniform attenuation over the frequency spectrum but still show better filtering performance in certain frequency ranges than in others.
A particularly important application for filtered electrical connectors are connectors for connecting vehicle control electronics with a squib or igniter of an air bag device. An electrical deployment signal is directed through the connector for actuating the air bag device. In absence of the deployment signal, it must be made sure that the air bag device in not inadvertently deployed by induced signals. Such signals may be induced, for example, by mobile telephones which transmit signals at particular frequencies such as 900 MHz, 1.8 or 1.9 GHz. Of course, in today""s environment filled with electronics, signals at many different frequencies may be induced and might cause actuation of the air bag device.
Another important consideration are spatial constraints. Miniaturization is an important trend in industry, and it is particularly important for connectors for air bag devices which are built into various places in automobiles where there is little space available such as the steering wheel, seat portions, or structural portions of the vehicle.
It is thus an important object of the invention to overcome one or more of the problems associated with prior art filter assembly or filtered electrical connectors.
Another object of the invention is to improve the filtering performance of filtered electrical connectors without substantially adding to the size and cost of the connector.
In order to attain the above objects, the present invention provides a filter assembly for filtering of electrical signals, comprising an electrical conductor for conducting an electrical signal to be filtered, at least two ferrite bodies, each of the ferrite bodies comprising at least two passages therein with the electrical conductor passing through said passages. Preferably, the filter assembly comprises two ferrite bodies, each having two passages therein. In a preferred embodiment, the ferrite bodies are of a generally cylindrical shape having a generally oval cross-section, wherein preferably the ferrite bodies are positioned adjacent to each other and the passages in the ferrite bodies are aligned in pairs. It is preferred that the passages are parallel to each other. Advantageously, the electrical conductor is passed through a first pair of the passages in a first direction and then through a second pair of said passages in a second direction opposite to said first direction. The ferrite bodies may be different in size, and/or may be made of materials with different filter performance.
According to another aspect of the invention, a filtered electrical connector is provided, comprising a connector housing made of an electrically insulating material, at least two terminals each having a cable contact area for conductively attaching cables for conducting a signal to be filtered and a contacting portion for making contact with a corresponding contacting portion in a complementary mating connector, and a filter assembly, comprising an electrical conductor for conducting an electrical signal to be filtered and at least two ferrite bodies, each of the ferrite bodies comprising at least two passages therein with the electrical conductor passing through the passages, with respective ends of the electrical connector being connected in series between one of the cable contact areas and an associated contacting portion. According to a preferred embodiment, the filtered electrical connector further comprises a frame made of electrically conductive material, said frame forming said at least two terminals. The filter assembly of the first aspect of the invention may be used in the filtered electrical connector of the second aspect of the invention. Preferably, the filtered electrical connector is an angled air bag connector.
This invention provides a combination of optimal filtering performance over a wide frequency range and small packaging size suitable in connector applications. Instead of one multiaperture core (connectors are commonly built with one material/one piece ferrite filter), this invention proposes a combination of ferrite filters consisting of two or more multiaperture cores using different ferrite materials and sizes to assure optimal filtering performance over a defined frequency range. The electrical signal is routed trough the ferrites using magnet wire. The magnet wire is resistance/sonically welded or soldered to the terminal frame. An advantage of this invention over prior art is superior filtering performance over a much wider frequency range in smallest possible packaging.